The invention relates to a hydraulic control system for controlling a plurality of consumers.
Hydraulic control systems of this kind are used particularly in mobile machines such as wheel loaders or tractors in order to supply pressure fluid to their consumers, e.g. the working hydraulics, the steering, traveling mechanisms, and/or accessories. DE 10 2006 008 940.5 has disclosed a hydraulic control system that is embodied in the form of an LS system. In an LS system of this kind, the delivery quantity of the pump is regulated so that in the pump line, a pump pressure prevails that lies a certain pressure difference □p above the maximum load pressure of the consumers. In the known systems, each consumer is associated with an adjustable metering orifice and an individual pressure governor by means of which the volumetric flow of pressure fluid to the consumer can be controlled as a function of the opening cross-section of the metering orifice, independent of the load. In this LS system, downstream of the pump, an inlet pressure governor can be provided, which can open a connection to the tank. This inlet pressure governor is acted on in the closing direction by a spring and by a control pressure that corresponds to the maximum load pressure and is acted on in the opening direction by the pump pressure. Its position is a measure of the difference between the pump pressure and the maximum load pressure.
In order to connect attachments or accessories that do not have their own supply of pressure fluid, a so-called power beyond connection is provided, which has a pressure line, a return line, and an LS line. This power beyond connection permits the load-sensing system of the machine to also be used for the accessory. The power beyond connection for connecting a power beyond consumer branches off from the pressure fluid flow path between the pump and the inlet pressure governor. Then one of the load pressures of the working hydraulics consumers or of a power beyond consumer exerts pressure on the inlet pressure governor on the spring side. This hydraulic control system permits a prioritized supply to the power beyond consumers and a boosting of the regulating pressure difference between the pump pressure and the maximum load pressure when supplying power beyond consumers. In this embodiment, the slow reaction behavior of the inlet pressure governor when the power beyond consumer is switched on or off can be disadvantageous and can lead to pressure pulsations in the hydraulic control system.